Engineering of UV-absorbing polypropylene films containing poly(2-(2′-hydroxy-5′-methacryloxyethylphenyl)-2H-benzotriazole) nanoparticles

Ultraviolet-absorbing nanoparticles (NPs) were prepared by emulsion co-polymerization of the vinylic monomer 2-(2′-hydroxy-5′-methacryloxyethylphenyl)-2H-benzotriazole (Norbloc™, NB) with the crosslinking monomer divinylbenzene. The effect of total monomer, surfactant, crosslinker, and initiator concentrations on the size and size distribution of the formed NPs was elucidated. The NB monomer and the formed polyNB (PNB) NPs of 19 ± 2 nm were then incorporated into polypropylene (PP) films by melt-compounding technique by using cast film extrusion. Increasing the PNB NP concentrations integrated within the PP films decreased their UV transmittance. Migration of the UV absorbing PNB NPs from the PP films was not observed during 3 years of storage at room temperature or while exposure to extreme conditions. Under the same conditions, a significant migration was observed for the NB monomer-containing films. Overall, the PNB NP-containing films are clear and transparent, although the haze was affected by the addition of NB and PNB NPs. Moreover, the films have good mechanical properties and UV-blocking quality.